The long term goal of this project is to understand the epidemiology of specific types of genital human papillomavirus (HPV) infection in young women. Though HPV is the most common sexually transmitted disease, and a major cause of morbidity and mortality, including venereal warts, squamous intraepithelial lesions (SILs), recurrent respiratory papillomatosis, and cancers of the cervix, vagina, vulva, penis, and anus, little is known about the virus as asexually transmitted infectious agent. Our findings to date suggest 1) an extremely high incidence rate of 25% per year among female University students, 18 to 20 years of age, 2) risk of infection is reduced by consistent condom use with all new partners, and 3) cytologic, colposcopic, and/or macroscopically visible lesions develop in 47% of women with recently acquired cervical HPV infection. In the proposed cohort study, we plan to focus on incident genital HPV infections in order to develop fundamental epidemiologic measures of infectivity, persistence, progression, and resolution. The following specific aims will be pursued: 1. Define rates and determinants (e.g., condom use, frequency of intercourse, partner characteristics, co-infection, OC use) of acquisition of specific types of genital HPV. 2. Among women with incident infection by specific,types of HPV, define the frequency, patterns, and determinants of persisting infection. 3. Among women with incident infection by specific types of HPV define the rate and predictors of squamous intraepithelial lesions (SILs), including high grade SIL. As with other projects included in this STD CRC proposal, findings from this study will provide a basis for developing optimal strategies for primary prevention (e.g., immunization, condoms, or sexual behavior change) and secondary prevention (e.g., screening and treatment) of and STD pathogen with serious consequences in the female reproductive tract (e.g., cervical cancer and other HPV associated epithelial neoplasms).